"Why should my heart think that a several plot, / Which my heart knows the wide world's common place?"

Why does my heart believe you to be mine alone, when it knows that you will have sex with anyone?

"Or mine eyes, seeing this, say this is not, / To put fair truth upon so foul a face?"

And why do my eyes, seeing you act promiscuously, deny that it is so?

"In things right true my heart and eyes have erred, / And to this false plague are they now transferred."

My eyes and heart are misled about all things that are actually true, and are now loyal to my dishonest mistress.

Why is he saying it?

The unflattering tone of this sonnet and the other sonnets to the dark lady are in contrast with the Petrarchan tradition of sonneteering, in which the addressed woman is represented as lofty, chaste, and unattainable. Sir Thomas Wyatt, whose works Shakespeare would have known, had already breached this tradition with poems such as The Lady to Answer Directly with Yea or Nay. However, while other poets had represented women as less idealistic, in this sonnet Shakespeare downright insults the object of his desire, calling her "common," like a prostitute, and a "false plague." This degrading tone implies that the love affair was, for the speaker, unpleasant and even shameful.

The idea of the poet's eyes and heart distorting what they perceive is reminiscent of Sonnets 46 and 47, in which they are "at a mortal war" but end up reaching a compromise regarding the perception of the fair lord. But while those sonnets describe the eyes and heart lying to each other in order to deprive each other of basking in the fair lord's beauty, here the eyes are the main perpetrators, leading the heart behind them; Cupid has "forged hooks" out of them to this end. Thus the poet is overcome by the "blind fool, Love," who is Cupid; he becomes blind himself in his inability to see the truth.

The theme of believing one thing while seeing or knowing another to be true is carried through to the next sonnet, which begins, "When my love swears that she is made of truth, / I do believe her though I know she lies." Here, the poet admits in line 13 that, "In things right true my heart and eyes have erred." The word "things" could refer to the dark lady, whom the poet believed to be "right true," or it could be the fair lord, who actually was "true," but whom the poet abandoned in favor of the dark lady. The term "things" also carried a sexual slang meaning.

Ship imagery is employed in line 6 to suggest the woman's promiscuity. The phrase "anchored in the bay" used with "ride," implies a man having sexual intercourse; in this case, it is "all men" that are allowed to have sex with the dark lady. But the subject of this phrase is "eyes," implying that the poet is only visualizing having sex with the woman; thus, "all men" could really mean "all men's eyes," and rather than literally having sex with her, all men are just fantasizing about it like the poet does. The "forged hooks" into which Cupid makes the poet's eyes would be used to hoist sails and rigging on a ship, as well.

This imagery of the sea is foiled by imagery of the land used in lines 9-10, which compare the woman to a plot of land. The poet's heart believes the woman to be "a several plot," or a private plot of land for only him to enjoy. But in reality, that land is "the wide world's common place;" the woman is actually available to all men, either because she does not return the poet's love and remains unattached, or because she is promiscuous. The second meaning is more likely, since the word "common" is often tied to "whore;" its use here implies that the woman acts like a prostitute, and would be terribly unflattering and offensive to her.